The production of wood which has been treated to inhibit biological decomposition is well known. The organisms causing wood decomposition include: basidiomycetes such as Gloeophyllum trabeum (brown rot), Trametes versicolor (white rot), Serpula lacrymans (dry rot) and Coniophora puteana; coleopterans such as Anobium punctatum (furniture beetle), Hylotrupes bajulus (house longhorn) and Xestobium rufovillorum (death watch beetle); and hyrnenopterans such as termites and carpenter ants. In 1996, 592 million cubic feet of pressure-treated wood was produced in the United States.
The major product of the industry is southern pine lumber treated with chromated copper arsenate (CCA). Most of this treated lumber is used for decks, fencing and landscape timbers. There is concern about the safety and health effects of CCA as a wood preservative. Alternative wood preservative systems for lumber, with lower perceived risk, such as ammoniacal copper quat (ACQ), copper bis(dimethyldithiocarbamate) (CDDC), ammoniacal copper citrate and copper azole, are also in limited commercial use.
Modern organic biocides are considered to be relatively environmentally benign and not expected to pose the problems associated with CCA-treated lumber. Biocides such as tebuconazole are quite soluble in common organic solvents while others such as chlorothalonil possess only low solubility. The solubility of organic biocides affects the markets for which the biocide-treated wood products are appropriate. Biocides with good solubility can be dissolved at high concentrations in a small amount of organic solvents, and that solution can be dispersed in water with appropriate emulsifiers to produce an aqueous emulsion. The emulsion can be used in conventional pressure treatments for lumber and wood treated in such a manner can be used in products such as decking where the treated wood will come into contact with humans. Biocides which possess low solubility must be incorporated into wood in a solution of a hydrocarbon oil such as AWPA P9 Type A and the resulting organic solution used to treat wood directly. Wood treated in this way can be used only for industrial applications, such as utility poles and railway ties, because the oil is irritating to human skin.
It would be desirable to find a means of applying a broad spectrum of organic biocides of varying solubility and activity to wood that avoids the use of irritating or toxic oils.
The invention provides a method for incorporating additives into wood or a wood product. The method comprises incorporating an additive into a nanoparticle, applying the nanoparticle to wood or a wood particle and applying sufficient pressure to force the nanoparticle to penetrate the wood or wood particle.
The invention further provides a method for incorporating additives into wood or a wood product. The method comprises incorporating a biocide into a nanoparticle, blending the nanoparticle into wood particles and applying sufficient pressure to form a wood product.
The invention further provides a method of inhibiting decomposition of wood or a wood product. The method comprises incorporating a biocide into a nanoparticle, applying the nanoparticle having the biocide incorporated therein to wood or a wood product and applying sufficient pressure to force the nanoparticle to penetrate the wood or wood particle.
The invention further provides a finished wood article or wood product comprising wood and a nanoparticle having a biocide incorporated therein. The nanoparticle is incorporated in the wood.